Oilproofed electrical conduit, insulation, etc.



Feb. 3, 193?. J KENNEDY 1,846,599

OILPROOFED ELECTRICAL CONDUIT, INSULATION, ETC

Filed Dec. 15. 1928 Patented Feb. 23, 1932 UNITED STATES- PATENT OFFICEJOSEPH A. KENNEDY, OF PAWTUCKET, RHODE- ISLAND, ASSIGNOR, BY MESNEASSIGN- IENTS, TO ANACONDA WARE WIRE AND CABLE COMPANY, A CORPORATION OFDELA- Application filed December 15, 1928. Serial No. 826,411.

The present invention relates to protective coverin s or jackets forelectrical conductors, w ether constructed and applied directly about abare or an insulated wire as an inseparable envelope, or made as an opentube or conduit adapted to be passed over, or to receive, a bare orcovered wire or cable; and, it is particularly concerned with flexiblejackets made of fibrous strands interconnected or interlocked byweaving, braiding, knitting, or otherwise. The object of the inventionis to give to protecting means of the character indicated not onlywater-resistant and flame-resistant qualities suitable for therequirements of the art, but-oil-resistant qualities as well.

The invention will be fully apparent from the following specificationand will be defined with particularity as required by the statutesin'the appended claims.

One embodiment of the invention is exemplified in Fig. 1 which is anelevation of an electrical conductor with portions broken away to revealinterior portions.

Fig. 2 exemplifies the invention embodied in a conduit adapted to bepassed over, or to receive, a bare or covered wire cable.

In the embodiment illustrated in Fig. 1, 10 are conductors, each ofwhich are covered with a water-proofing coating 12 such as .asphaltum.This coating is in turn covered with a flexible jacket 14 which has acovering of a flame-proofing compound such as stearin pitch impregnatedtherein. Over this layer, there is applied, in a manner here inafterdescribed, a film or coating of a substance which isinsoluble insolvents of the stearin pitch. While not limited thereto this insolublecoating of film may constitute a homogeneous or continuous fihn ofsodium. silicate which can be conveniently applied in.

the form of an aqueous solution. If desired, this solution may beimpregnated in an outer jacket 16. Over the layer or film of sodiumsilicate, there is applied a thin layer or coating of cellulosiclacquer. As shown in Fig. 1,

a pair of cables having the protective coating herein described may beenclosed in an outer sheath comprising the layers a, b, c and d. Theinnermost layer a being impregnated or coated with a water-proofingcompound such as asphaltum or the like to which is applied a layer offlame-proofing material indicated at 12. Over this there is a layer ofsodium silicate or similar material which is insoluble in the solvent inthe flame-proofing material. Over the layer 0, there is applied a. layer03 of suitable lacquer having oil resisting properties.

Fig. 2 illustrates the invention applied to a hollow tube or conduithaving layers a, b, 0 and d which are substantially the same as ghecorrespondingly identified layers of Incarrying the invention intoeffect, I first treat the protecting jacket with a waterproofingcompound or agent; preferablyusing asphaltum for this purpose, althoughI do not limit myself to that specific material. The asphaltum or otherwater-proofing substance may be applied in either melted condition or insolution with a volatile solvent in any known or other suitable manner.I next apply to the outer surface of the protective jacket a coating offlame-proofing compound, preferably stearin pitch rendered fluid byheat; although here again I am not narrowly limited to a specificmaterial. The above named compounds have long been known and commonlyused for treating both open conduits formed of interwoven flexiblestrands and conductors and cables on which fibrous braided, knitted orwoven jackets have been built. They may be applied for the purposes ofthe present invention by immersing the fabric in tanks containing thefluid compounds, or in any other manner already known or which may behereafter devised.

In the further carrying out of the invention, the treated jacket orjacketed conductor is coated with sodium silicate, preferably and theadherent film is allowed to dry, either by exposure to the surroundingair for a sufficient length of time, or more rapidly by passing throu ha heated oven or in exposure to other suita le heating means.

When the film of sodium silicate is sufficiently firm, the oil-proofingtreatment is carried out by coating the article with cellulosic lacquer,as nitrocellulose, cellulose acetate, or other cellulose compound whichis capable of being provided in dissolved condition and has the desiredoil-resistant properties. Inasmuch as it is desirable to produce thefinished article at as low cost as possible, I prefer to use the leastexpensive compounds of cellulose and solutions of such compounds whichwill serve the purpose. From this point of view, nitrocellulose ispreferable to other cellulosic compounds, and the less expensive of theknown suitable solvents of nitrocellulose are used todissolve it and todilute the solution. Any of the known softeners 0r emollients forcellulosic compounds may be included in the lacquer in order that thecoating when dried may be sufficiently elastic and flexible. The lacqueris likewise preferably applied by passing the conduit or jacketedconductor through a body of the lacquer solution in a tank, wiping. oflthe excess as the article emerges from the tank, and drying the residualfilm. Two or more such films may be thus applied in succession in orderto build up a coating of the required thickness. This lacquer coatingstep is the final step in producing the finished article.

The jacket thus produced is resistant to penetration by water and oiland to'ignition by flame. Preferably the initial waterproofing compoundis applied in such a way as substantially tosaturate the constituentstrands so that they will not absorb moisture either from water cominginto direct contact with the'structure or from vapor in the atmosphere.Both the flame-proofing coat of stearin pitch and the lacquer coat arealso impervious to water and form external waterrepellent means; thelacquer coat also protecting the film of sodium silicate from attack anddissolution by water. Both the film of sodium silicate and the outercoat of lacquer protect the jacket against attack by oil, which is asolvent of asphaltum, stearin pitch and other hydrocarbonaceousmaterials used for initial water-proofingand flameproofing. Thus myimproved jackets are suitable to protect electrical conductors used inautomobiles in the vicinity of the engine,

or other situations where they are liable to be'spattered or coveredwith oil.

While some cellulose compounds which may be used as the basis ofoil-resistant lacquer are relatively non-inflammable, others, includinnitrocellulose, are highly inflammable. owever, even nitrocellulose usedin this environment does not constitute a fire hazard because it isapplied in such athin coat that, even if ignited, it does not generateenough heat to have any effect on the flame-proofing compound.

The flame-proofing effect given by stearin pitchis augmented andenhanced by the film of sodium silicate on the pitch coating. The valueof stearin pitch as a flame-proofing agent arises from the fact that,although it is not incombustible, it nevertheless contains but a smallproportion of inflammable matter and is ignited only with difficulty,and when ignited it quickly forms a porous or blisterlike ashimprisoning inert gases which have heat insulating effect about theenclosed conductors and the inflammable insulation thereof. And evenwhen the pitch coating is ignited in one part of the fabric by intenseheat, the flame is soon extinguished and does not travel along thejacket from the heated part. But even such slight combustion as stearinpitch undergoes when exposedto flame is largely prevented by the outerfilm of sodium silicate, which is wholly incolnbustible and excludes airfrom the enclosed stearin pitch.

In addition to its oil-proofing and flameproofing qualities abovedescribed, the sodium silicate film likewise protects the asphaltum andflame-proofing compound from attack by the solvents in the lacquersolution. Many thinners Which-I prefer to use on account of their lowprice have so powerful a solvent action on stearin pitch that the latteris liable to be softened by the solvents and impermeated. by thenitrocellulose, during its immersion in the lacquer bath, to such anextent as to diminish seriously its flameproofing capacity. But sodiumsilicate is insoluble in the lacquer solvents and wholly protects allparts of the stearin pitch coat which it covers from attack by thesesolvents.

However, it is desirable to effect a commingling to some extent of thelacquer coating with the pitch coating in order to anchor the lacquercoating firmly to the jacket so that it cannot be readily peeled ofl ifit should be injured by abrasion. Hence I prefer to apply the sodiumsilicate in such a thin solution, or wipe off so much of the adherentsolution while still wet that the high points of the jacket will be bareof the silicate and hence subject to attack by the lacquer solvents.Fabricated jackets of the type with which this invention is particularlyconcerned are more or less rough on the outside where theirinterconnected strands cross one another, and such roughness remains insome measure after the fabric has emerged from the fiame-proofing bath.Hence by wiping it when it leaves the bath of sodium silicate solution,the high points are left with little or no sodium silicate upon them.Thestearin pitch at these oints is softened by the lacquer solvents andcomes interlocked and bonded" with the lacquer coating when the latterhas dried. Thus the lacquer coat is securely attached to the fabric atdiscontinuous points while being excluded from penetration into thestearin pitch coat over most of the surface of the fabric.

While the article thus described in detail is the preferred embodimentof the invention, modifications and variations may be made withoutdeparting from the spirit of the pitch coating invention or the scope ofthe appended claims. For instance, the entire surface of the stearin maybe covered with sodium silicate if it is desired to extend theflameproofing qualities imparted by the latter to all points.

The term jacket as used in this specifica tion is intended to includeboth independent conduit or tubing adapted to receive conductors, andenvelopes formed originally upon insulated wires or cables and embracingthe same so closely as to be practically immovable thereon. Anillustration of a suitable structure for such 'ackets is iven by thepatent to Charles Smith, 1%0. 1,016,527, February 6, 1912. However, theinvention is not limited to jacketsof this particular construction butincludes those made of an other materials and in any other way whic maybe advantageously treated in accordance with the rinciples hereinbeforedescribed.

What f claim and desire to secure by Letters Patent is:

1. A jacket for the protection of electrical conductors having aflame-proofing coat, an outer oil-proofing coat, and an intermediatehomogeneous coat of a substance which is insoluble by the solvents ofthe flame-proofing and oil-proofing coats.

2. A protective jacket for electrical conductors having a flame-proofingcoat, an outer coat of oil-proofing material bonded at separated pointsto the flame-proofing coat, and an intermediate homogeneous film ofmaterial which is insoluble in the solvents of the before named coatsinterposed between said coats where the latter are not thus bondedtogether.

3. A protective jacket for electrical conductors having a flame-proofingcoat of stearin pitch, an outer coat of cellulose lacquer, and anintermediate coat of sodium silicate.

4. A protective jacket for electrical conductors having a protectivecoating, an outer coat of oil-proof lacquer and an intermediate film ofa. substance which is insoluble by the solvents of the first named coat.

5. -A coatedjacket for electrical conductors having coatings ofdiiferent materials, com- I prising an outermost oil-proof coat which isthe residue of an originally fluid solution, an

innermost coat which is a substance somewhat soluble in the solvent ofsaid solution, and an intermediate homogeneous coat comprising asubstance which is the substance which forms the outermost coat.

6. A protective jacket for electrical conductors having a flame-proofingcoat of stearin pitch, an outer coat of cellulose lacquer, and anintermediate coat of sodium silicate, said intermediate coat beingpenetrated at isolated points by the stearin pitch coat, and the saidcoats of stearin pitch and lacquer being bonded together by comminglingat such points.

7. A water-, oil-, and flame-resistant protective jacket for electricalconductors comprising a fabric having an impregnation of asphaltum, acoat of stearinpitch on its exterior, a film of sodium silicate outsideof the last named coat, and a coat of cellulose lacquer outside of all.

8. The method of flame-proofing and oilinsoluble-by the solvent ofproofing protective jackets of and for electrical conductors whichcomprises coating the jacket with a flame-resistant compound, applyingon -said compound an aqueous coating of non-combustible material whichis insoluble by the common solvents of the flameproofing coat and theafter mentioned oilproofing coat, and finally applying an outer coat ofa lacquer which is insoluble in oil, in solution with a'volatilesolvent, and drying said outer coat.

9. The method of flame-proofin and oilproofing protective jackets of andor electrical conductors which comprises coating the jacket with aflame-resistant compound, applying on said compound an aqueous solutionand drying it to form a coat of non-combustible material which isinsoluble by the common solvents of the flame-proofing coat and theafter mentioned oil-proofing coat in such manner that isolated pointsofthe first coat are substantially free from the material of the secondcoat, and applying an outer coat of lacquer in solution with a solventwhich is also a solvent of the first named coat, whereby the lacquerbecomes commingled and bonded with the first coat at the points whichare not covered by the second coat, said lacquer being insoluble by oil.

10. The method of oil-, water-, and flame proofing jackets of and forelectrical conductors which comprises coating the conductor withliquefied stearin pitch, applying an aqueous solution of sodium silicateupon said stearin pitch coat, drying such solution, and finally applyingcellulose lacquer dissolved in a volatile solvent to the jacket anddrying the lacquer coat.

11. The method of 'oil-, water-, and flameproofing jackets of and forelectrical conductors which comprises coating the jacket with meltedstearin pitch, applying a water solution of sodium silicate outside ofthe stearin pitch coating and leaving isolated points of the latteruncovered by said solution, drying the sodiumsilicate coat, and finallycoating the acket with a cellulose compound in solu- 5 tion with asolvent Which is also a solvent of steal-in pitch, and; drying the lastnamed;

coat.

nature.

In teetimony whereof l have affixed my slg- JOSEPH A. KENNEDY

